Effective HAZOP analysis and SWIFT method for process safety and risk management
HAZOP means Hazard & Operability. During a HAZOP analysis, the hazards of (sub) processes are mapped out in a structured manner. Towards the end of the design phase, the HAZOP method is very suitable for removing unforeseen errors from the design, but it can also be a useful tool during other phases to understand a process design with the team.
Preparing for the HAZOP
Steps to prepare for the HAZOP:
- Putting together a team
For a successful HAZOP analysis, it is essential to have a well-composed team. This team can consist of a HAZOP leader, note taker/scribe, project leader, process technologist, QA member, EIA engineer, operators, machine supplier, SHE, TD and a specialist in, for example, steam or refrigeration technology.
- Schedule sessions
The HAZOP analysis is carried out during one or more group sessions. A HAZOP session can be very intensive. Therefore, hold the sessions in a well-lit room with sufficient ventilation and plan sessions of a maximum of 4 hours per day with two short breaks.
- Collect documentation
Frozen files such as P&ID and FDS are crucial. Depending on the project, other information such as layouts marking hazardous areas or high traffic areas, manuals, electrical and pneumatic drawings, photographs and safety data sheets may also be valuable.
- Divide the process into nodes
This step in the HAZOP analysis requires frozen P&IDs, PFDs, or other visual representations of the process under review. The process is divided into sub-processes, these are called the nodes.
The size of the node depends on the complexity of the system. Nodes that are too small lead to unnecessary documentation and possible repetition, while nodes that are too large can become complex and unclear, potentially overlooking dangers.
Process conditions, such as flow, pressure, temperature and materials, are also recorded to determine complexity.
During the HAZOP analysis
At the start of the HAZOP analysis, the documents are distributed by the HAZOP leader and a short introduction is given explaining the HAZOP methodology. If not all participants are familiar with each other, a short introduction round will take place. The engineer of the process to be assessed explains the operation of the system. The HAZOP leader guides the team using guide words such as: pressure, flow, temperature and deviations such as: more, less, opposite, through the nodes.
The stated naked risks are assessed for “probability x effect” using a risk matrix.
Below, control measures that are present in the design are mentioned and the risk is reassessed. If it appears that the risk is not sufficiently under control (score higher than 7), actions are formulated or the risk is accepted. At the end of the HAZOP session, the note taker/scribe shares a report and action list with the relevant responsible parties. If desired, a new contact moment can be scheduled after an agreed number of weeks to check whether the actions have been carried out.
SWIFT method
If HAZOP is not mandatory, you can consider applying a SWIFT method to understand (sub)processes. SWIFT stands for Structured What If Technique.
This methodology requires better preparation than the HAZOP analysis and therefore more preparation time. This makes the brainstorming session itself shorter. The SWIFT leader, in collaboration with the customer, draws up a checklist with topics such as material/product, external influences, utilities and instrumentation. A number of scenarios are listed per topic and, just like with a HAZOP analysis, nodes are made of the process.
SWIFT Brainstorming session: questions, risks and control measures
At the start of the brainstorming session, the process is explained by the engineer responsible for the design. The team then formulates questions per node, which often start with “What if…” or a similar formulation, such as “Is it possible that…”. For example, consider a question such as “What if the cooling water disappears?”
The SWIFT leader can provide additional suggestions and topics using the checklist. Once the questions have been formulated, the note taker/scribe will read out the questions one by one. The team identifies the risks for each question and indicates which ones, and whether sufficient control measures are in place. If this is not the case, actions are noted or the risk is accepted.
An action list and report are shared. As with the HAZOP method, if desired, a new contact moment can be scheduled after an agreed number of weeks to check whether the actions have been carried out.